1. Field of Invention
The present invention relates to a paper pressing device, and more particularly to a paper pressing device which is able to press the paper sheet by surface contact for maintaining a paper sheet flat while being scanned.
2. Related Art
Due to the development of business, demands of printers and scanners have been increasing rapidly. At present, the design of a printer or a scanner trends to include multiple functions, i.e., a multi-function peripheral (MFP) providing more than one functionality such as print, image scan, document fax, document copy, even card read, and so on. With the continuing development of MFP, the price of MFP is being reduced gradually due to the commercial competition, so that students and families in addition to companies or organizations have become users of the MFP.
For automatic paper feeding mechanisms of a scanner or an MFP, a narrow space is provided above the scanning module for a paper sheet passing through while the paper sheet passes over the scanning module. In order to obtain a favorable quality of scanning images under the high-speed movement of the paper sheet, a paper pressing mechanism is provided to press the paper sheet onto the surface of a transparent plate of the scanning module, for maintaining the paper sheet flat. Further, in order to perform color correction, a color reference slice is provided to be scanned by the scanning module, and then the scanning module captures the image of the color reference slice, and then corrects the image data of the paper sheet with the color and color level of the color reference slice as a correction reference.
FIG. 1 is a sectional view of a scanning apparatus with a paper pressing device in the prior art. The paper pressing device has a pressing plate 131 and a spring 132. The scanning apparatus has a first body 110 and a second body 120. A paper track 150 is formed between the first body 110 and the second body 120 for a paper passing through. The first body 110 is mainly the upper portion of the scanning apparatus and the second body 120 is mainly the lower portion of the scanning apparatus, in which a scanning module 121 is disposed on the second body 120. A transparent plate 122 is disposed on the second body 120 and located above the scanning module 121, wherein the transparent plate 122 is made of light transparent materials, such a glass or reinforced plastic. The pressing plate 131 is pivotally connected to the first body 110, and the spring 132 is provided for pushing the pressing plate 131 swiveling toward the transparent plate 122, so that the pressing plat 131 presses against the paper sheet which passes over the transparent plate 122, to maintain the paper sheet flat on the surface of the transparent plate 122. Thereby the paper sheet can be scanned by the scanning module 121 with a favorable optical condition and preventing the scanning quality from being negatively affected due to the paper sheet being wrinkled.
However, the paper pressing device in the prior art has the following disadvantages.
1. The flatness of the pressing plate 131 is poor and a deformation is more likely to occur when pressing plate 131 is manufactured.
2. A plurality of springs 132 is required to overcome the problems of poor flatness and deformation of the flattening plate 131, and it is difficult for the paper pressing device to generate a uniform forward pressure.
3. An exclusive color reference slice 123 has to be used to correct the image data of the paper sheet with the color and color level.
FIG. 2 is a sectional view of another scanning apparatus with a paper pressing device in the prior art. The paper pressing device is a film 241 made of plastic. The scanning apparatus has a first body 210 and a second body 220. A paper track 250 is formed between the first body 210 and the second body 220.
The first body 210 is mainly the upper portion of the scanning apparatus and the second body 220 is mainly the lower portion of the scanning apparatus, in which a scanning module 221 is disposed in the second body 220, and a transparent plate 222 is disposed on the second body 220 and located above the scanning module 221. The film 241 can be elastically deformed to press the paper sheet onto the transparent plate 222 for maintaining the paper sheet flat. However, the film 241 still has the following disadvantages.
1. An exclusive color reference slice has to be used to correct the image data of the paper sheet with the color and color level.
2. Since only the free end at the front edge of the film 241 contacts the paper, the film 241 presses the paper sheet by linear contact instead of surface contact, and thus it is difficult to effectively maintain the paper sheet flat on the transparent plate 222 to be scanned by the scanning module 221.